28 



Fishery Bulletin 105(1) 



were examined. Examination of ovaries of prespawn- 

 ing females alone would lead to the assumption that 

 the potential fecundity is close to the realized fecun- 

 dity. Atresia in postspawning Atka mackerel has been 



CO 



CD 



D 



B A 



* 1 A 1 * u *-^ 



D D D B 



■n  



D D 



Length (cm) 



Figure 6 



(A) Model fit and 95% confidence intervals for potential fecundity of 

 Atka mackerel {Pleurogrammus monopterygius) at length for total 

 number of oocytes (solid lines), stage-5+ oocytes (short dashed lines), 

 and realized fecundity (long dashed lines). (B) Data and model fit 

 (line) for Atka mackerel batch fecundity by length. (C) Data and model 

 fit for number of atretic oocytes in spent ovaries of Atka mackerel 

 by length. (D) Number of batches spawned by length for potential 

 fecundity (solid triangles) and realized fecundity (open squares) and 

 the estimated population means (solid line for potential fecundity 

 and dashed line for realized fecundity) for Atka mackerel. 



described in earlier studies (Gorbunova, 1962; Zolotov, 

 1993), where 400-500 atretic eggs per ovary and the 

 prolonged presence of atretic eggs in the ovaries before 

 reabsorption have been reported. However, this is the 

 first study where atresia from recently spent 

 ovaries has been included in the fecundity 

 analysis in a quantitative manner. When 

 recently spent ovaries were examined, it 

 appeared that atresia had a major effect 

 on potential fecundity and that an aver- 

 age of 1-2 batches were reabsorbed at the 

 end of the spawning period in the ovaries 

 examined. It should be noted that specimens 

 with ovaries in the prespawning phase and 

 specimens with recently spent ovaries were 

 collected in different years. Atresia is likely 

 to be related to feeding ecology, availability 

 of appropriate substrate and environmental 

 conditions for spawning, and could poten- 

 tially change from year to year. Interannual 

 variability of atresia should be examined in 

 the future. 



Acknowledgments 



We thank G. Thompson and J. lanelli for 

 their statistical advice and F. Morado for his 

 advice and assistance with histological work. 

 We also thank all the observers and scientists 

 who collected specimens and the commercial 

 fishing industry for providing sampling plat- 

 forms. G. Stauffer, B. Miller, A. Hollowed, 

 S. Lowe, and S. Hinckley helped greatly by 

 critically reviewing drafts of this paper. This 

 research was supported by the Joint Institute 

 for the Study of the Atmosphere and Ocean 

 (JISAO) under NOAA Cooperative Agreement 

 no. NA67RJ0155 (contribution no. 986). 



Literature cited 



Gorbunova, N. N. 



1962. Spawning and development of 

 greenlings (family Hexagrammidae). In 

 Greenlings: taxonomy, biology, interoce- 

 anic transplantation (T. S. Rass, ed.), p. 

 1-103. Tr. Inst. Okeanol., Akad. Nauk. 

 SSSR 59:118-182. In Russian (translated 

 by Isr Program. Sci. Trans., 1970). [Avail- 

 able from Natl. Tech. Inf Serv., Springfield, 

 VA, as TT 69-55097 S.] 



Hardardottir, K., O. S. Kjesbu, and G. Marteinsdottir. 

 2001. Atresia in Icelandic cod (Gadus morhua 

 L.) prior to and during spawning. Report 

 of the working group on modern approaches 

 to assess maturity and fecundity of warm- 

 and cold-water fish and squids (O. S. Kjesbu, 

 J. R. Hunter, and P. R. Withames, eds.), 140 

 p. Institute of Marine Research, Bergen, 

 Norway. 



